I know, it sounds crazy, but this is WoT balance for you.
All WT missions are for damage and kills, none for victory. And this is not one of those posts suggesting you go afk or drown out of pity for harriers.
You can absolutely wipe the floor with them and still not go full power trip to deny them a win:
your missions as WT require damage and kills, focus on what you need during the battle
don’t focus cappers (harriers that take plasma to generators), this is a sure way to end the battle early (you “win” but you get less damage and kills because time expires)
if it’s a good harrier team and you still have missions to complete, by all means do your best
if it’s one of the other 95% of the harrier teams that have a few less-informed players, farm them but don’t deny them damage: don’t camp the generators, don’t focus plasma carriers, don’t use hard cover or teleport at the edge of the world to escape
At the end of the day, this should be a fun game mode. I only had 7 keys played so far, but every time i managed 10-15 kills and 15k+ damage as Waffentrager by doing the things above.